The invention relates to a method of measuring the optical radiation energy reflected by a reflection place as a relative fraction of energy supplied by an optical transmitter via an optical line.
In a method of this type known from "International Electronical Commission, Technical Committee 86, Subcommittee 86B: Draft Publication YYY: Generic Specification for Fibre Optic Branching Devices-Optical Tests-Return Loss" the energy supplied to the reflection area and its reflected fraction must be determined by means of two successive measurements. Measuring errors are produced when the reception characteristic is changed, for example, due to long-time influences or temperature fluctuations. Furthermore, the known method must ensure stability and reproducibility of the properties of optical elements used, particularly directional couplers or connection elements.